Effects of carcinogen dose on the characteristics of the tracheal tumor response induced by N-nitroso-N-methylurea in hamsters
✍ Scribed by Tsutomu Yarita; Paul Nettesheim
- Publisher
- John Wiley and Sons
- Year
- 1978
- Tongue
- French
- Weight
- 513 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
Tracheal tumors were induced by repeated intratracheal exposures to the carcinogen N‐nitroso‐N‐methylurea (NMU), using a catheter system previously described. Carcinogen concentrations of 0.25, 0.50 and 1.0% were employed in 20 or 30 twice‐weekly exposures. Most of the tumors developed in the mid‐portion of the tracheas. Virtually all tumors developed after the end of the 10‐ to 15‐week exposure period. Tumor incidence ranged from 20–94% with mean tumor induction times of 13–46 weeks, depending on NMU concentration and frequency of exposure (i.e., dose). At lower doses, mostly non‐invasive tumors were induced; at higher doses, mostly invasive carcinomas of various histological types (epidermoid, adeno‐, epidermoid‐adeno, and anaplastic large‐ and small‐cell carcinomas) were induced. Adenocarcinomas were most frequent at low NMU concentrations. The possible mechanisms of the carcinogen dose effects are discussed.